Fine feed distortion arrangement for grinding machines



March 1, 1960 A. L. KRAUSE ET AL 2,926,457

FINE FEED nsToRTIoN ARRANGEMENT FoR GRINDING MACHINES 3 Sheets-Sheet l Filed Jan. l0, 1958 March 1, 1960 A. l.. KRAUSE ET Al. 2,926,467

FINE FEED DISTORTION ARRANGEMENT FOR GRINDING MACHINES s sheets-sheet 2 Filed Jan, 1o, 1958 f will/mmf@ 620 JL/awww lf ff/ M March l, 1960 A. L. KRAUsE ET AL 2,926,467

FINE FEED DISTORTION ARRANGEMENT FOR GRINDING MACHINES Filed Jan. 1o, 195e 5 Sheets-Sheet 3 FINE FEED DISTORTION ARRANGEMENT FOR GRINDING MACHINES August L. Krause, Cranston, and George N. Levesque, Warwick, RJ., assignors to Brown & Sharpe Mfg. Co., Providence, RJ., a corporation of Rhode Island Application January 10, 1958, Serial No. 708,216

7 Claims. (Cl. 51-165) The present invention relates to a fine feedcontrol for a machine tool, and is herein disclosed as embodied in a grinding machine of the general type having a base, a work supporting table carried on a forwardly extending portion of the base for movement in a transverse direction, and a grinding wheel carriage mounted rearwardly of the table on ways for movement in a forward and back direction. Cross feeding movements may be imparted to the `grinding Wheel carriage by means of a handwheel which operates through a feed screw rotatably mounted in the base and a nut threaded thereto which is secured to the underside of the carriage.

It is a principal object of the present invention to provide a novel and improved device for subjecting selected portions of the machine supporting structure to controlled stresses which will have the effect of imparting a, slight additional relative feeding movement between theA grinding wheel'and the work support which is in the nature of a reduced finishing feed.

In accordance with the-invention a controlled bending strain is applied t-o the machine bed or base on which are mounted the grinding wheel carriage and work supporting table which is effective to effect a'slight resilient distortion of the base and thereby to impart a small additional increment of relative feeding movement between the grinding wheel and work which is a fraction only of the finest increment of feeding movement obtainable by adjustment of the conventional feeding devices.

The several features of the invention together with the advantages to be obtain thereby will be more fully described in connection with the accompanying drawings in which: v

Fig. 1 is a view in left side elevation of a slain grinding machine embodying in a preferred form lthe several features of the invention;

Fig. 2 is a view in front elevation of the grinding machine shown in Fig. l;

Fig. 3 is a sectional plan view taken on a line 3 3 of Fig. 2 illustrating particularly the shape of the machine bed provided with a knee-hole aperture for the operator and having a three-point support with the base section of the machine;

' Fig. 4 is a detail view partly insection looking from the left and on an enlarged scale of the mechanism for applying a regulated bending strain to the machine base and thereby for imparting a slight additional increment of feed to the grinding wheel; A

Fig. 5 is a view in front elevation partly in section of substantially the parts shown in Fig. 4;

Fig. 6 is an enlarged detail sectional view of the manual push control for actuating said auxiliary feed device for applying a slight additional increment of feed to the grinding wheel; Fig. 7 is a diagrammatic sectional view taken on line 7-7 of Fig. 3 to illustrate the relationship of the grinding wheel bed, the wheel carriage, the work table,` and the supporting base; and

Figs. 8. and 9 are ytwo views .illustrating an-alternative nited States Patent M mais? Patented Mar. 1, 1969 ice form of the invention as applied to a machine not having the knee-hole aperture, and in which a bending strain is appliedagainst the front and rear faces of the machine base having a tendency to spring these portions of the base outwardly and thus to cause the top portions of the base carrying respectively the work table and the grinding wheel carriage to be moved slightly toward one another;

Fig. 8 being a view in elevation looking from the right, partly in section of the machine, illustrating a mechanism for applying said bending strain;

Fig. 9 is a diagrammatic view illustrating the hydraulic mechanism employed for effecting a bending distortion of the machine base shown in Fig. 8; and

Fig. 10 is a fragmentary view in right side elevation illustrating the application of a gauging device to the machine for measuring work diameter as the work is brought down to size by the grinding operation.

It has been found that for extreme accuracy in grinding to Size themovement of the wheel slide to a precise fini-sh grinding position by the normally available mechanical means including the h-andwheel is subject to appreciable errors which are due to such factors as wind-up, backlash, and tensioning strains on the parts, which limit the efficiency of the normal feed mechanism.

In accord-ance with the invention the foregoing difficulties are avoided by means of a supplemental device which is independent of the cross feed mechanism and which Vserves to distort the base or bed of the machine on which both the Work and grinding wheel are carried so as to -throw the wheel axis and the work axis relatively toward each other by a very slight amount which can be read on a precise indicatingjmeans associated with the work gauge, so that there is a-'direct control of the amount distortion effective to produce a desired size of work.

Referring more particularlyto Figs. 1 to 7 inclusive of the drawings the invention is disclosed as embodied in a small knee-hole type plain grinding machine having a base 20, and mounted thereon, a bed 22.

A transversely extending way 24 formed on a forwardly extending portion of the bed provides support for a transversely movable work supporting table 26 on which are mounted a headstock 28 and footstock 30 adapted to receive between centers a cylindrical work piece such as that designated for example at 32 in Fig. 2. The headstock 28 includes a spindle 33 which is driven by means of an electric motor 34 and a V-belt 36 arranged to pass around pulleys on the armature shaft of the motor 34 and the shaft center of the headstock spindle 33.

There is also mounted on the bed 22 rearwardly of the table 26 a grinding wheel carriage 40 supported for forward'and back sliding movement on suitable ways formed on the machine bed 22. The carriage 40 provides support for a transversely extending grinding Wheel Spindle 42 and a grinding wheel 44 which is continuously driven by means of a belt 46 from an electric motor 48 carried on a bracket 50 on the grinding wheel carriage 40.

The wheel carriage 40 is moved back and forth on its ways by means of a feed mechanism which may be of conventional design including a nut 54 secured to the underside of the wheel carriage 40 and having a threaded engagement with a feed screw shaft 56 rotatably mounted on the bed 22. A pinion 58 on the feed screw shaft S6 meshes with a pinion 60 carried on a feed handwheel shaft 62 which is connected at its outer end with a feed handwheel 64.

The plain grinding machine illustrated in Figs. 1 to 7 is of the general type having a knee-hole aperture 66,

comprising a recess 67 formed in the base 20 and a recess 68 superimposed thereon formed in the machine bed 22. As best shown in Figs. 3 and 7 the bed 22 has a three-point support on the base 20 which consists of two supporting posts 70 and 72 which are mounted respectively at the right land left hand forwardly extending corners of the bed and base at each side of the knee-hole aperture. A third support post 74 providing a third point of support for the bed on the base 20 is provided at the extreme rear edge of the bed and base assembly.

In accordance with the invention a device is provided for drawing together by a very slight amount portions of the bed 22 and the base 20 disposed within the knee-hole aperture, which has the effect of causing the central portion of the bed 22 to be distorted downwardly and the grinding wheel and work thus to be brought very slightly toward one another. The deflection producing device comprises a bar 80 which is mounted on block 82 secured by screws 84 to the face of the knee-hole aperture recess 67 in the base and extends upwardly in close proximity to a bracket S6 rigidly secured by screws 88 to the face of the recessed portion 68 of the bed 22. A notch 90 formed in the post 80 is arranged to be engaged by the horizontally disposed upper surface of a fulcrum lever 92 pivoted on a ledge 94 formed in theV bracket 86. An upwardly extending portion of the fulcrum lever 92 is slotted to receive a spring arm 98 which acts when moved outwardly to the left from the position of Fig. to bias the fulcrum lever 92 counterclockwise so that the middle portion of the bed 22 is distorted downwardly by a predetermined small amount which is dependent upon the spring strength of the spring arm 98.

The mechanism for actuating the spring arm 93 and fulcrum lever 92 comprises a flexible wire 100 mounted within a sheath 102, which sheath is secured at one end to theupper end of the post 80, and at its other end to the front` wall of the bed 22. The flexible wire 100 mounted within the sheath is guided through an aperture in the post 80 and is arranged also to pass through a small aperture 'in the spring plate 98. A washer 104 is secured to the 4wire 100 between the post 80 and spring plate 98 so that a rearward thrust vof the wire 100 will flex the spring plate 98 outwardly to the left from the position of Fig. 5. At its other or forwardend the wire 100fis connected with a manually operable push knob 106 mounted on the front face of the machine bed 22. As best shown in Fig. 6 the stem of the push knob 106 extends within a tubular member 108 which is secured by a fitting 110 to the wall of the bed 22. A small compression spring 114 coiled about the wire 100 between the block 112 and sleeve fitting 110 acts to hold the push knob 106 and wire 100 in the normally withdrawn inoperative position of Fig. 6. An inward movement of the pushknob 106 acting through the wire 100 and washer 104 causes the spring arm 98 to be flexed outwardly to the left 'rocking the fulcrum lever 92 in a counterclockwise direction so that the ledge 94 on which lever 92 is fulcrummed is pressed downwardly against the corresponding upward pressure applied to the post S0 under a pressure which is determined by the strength of the spring arm 98.

Referring to Figs. 8 and 9 an alternative form of device for effecting a resilient deformation of the base of a grindingmachine, and thereby a final increment of relative feed of the grinding Wheel and work, isvshown which is particularly yadapted for use in a grinding machine having a unitary base 116 with front and rear walls y118, 120 and horizontally disposed tie members or plates spaced one adjacent the floor level designated at 122 and th'e other atva'substantially higher-level. designated at 124 butfsomewhat below the level ofthe tableand grind-Y ing wheel ways. Y

The distortion device illustrated in Figs. 8 and 9 comprises specically Aa plunger 126 which is Aarranged vat one end to bear against the front wall 118 ofthe grinding machine base 116 and at its other end is secured to avpiston 128 of a hydraulic cylinder 130 secured to the rear wall of thegrinding machinebase 116. Fluid-under pressure is admitted to the cylinder 130 through a supply line 132 and acts to impart a spreading strain to the front and -rear walls of the base 116 between the bottom tie member 122 of the base and the more upwardly located tie'member 124 of the base with the result that the upper portion of the base is slightly contracted causing the grinding wheel and the work to be moved slightly toward one another. The hydraulic connections by means of which a bending strain is applied to the base 116 of a predetermined amount is particularly illustrated by the hyraulic diagram of Fig. 9. The supply line 132 referred to is connected with a manual control valve 138 mounted on the front panel of the machine. The valve 13S comprises a housing and an axially shiftable valve body 140 having spool portions 140a and 14011 and an intermediate cut-away portion. The valve body 140 is fitted at its outer end with a push knob 142 and at its other end is arranged to be acted upon by a compression spring 144 which acts normally to move the valve body 140 to the left to a normally inoperative position. The hydraulic system includes a reservoir 146, a pressure line 148 from the reservoir to the valve 138 in which there is mounted a gear pump 150, and an exhaust line 152 from the valve 138 to the reservoir 146. The pressure line 143 and exhaust line 152 are connected by a cross line 156. The

- pressure in the system is controlled by means of a relief valve 158 in the cross line 156 and by an additional low pressure relief valve 160 in the exhaust line 152. For the disengaged position of the valve shown in Fig. 9 the reduced center portion 160 of the valve body 140 is positioned to connect the supply line 132 to the cylinder 128 with the exhaust line 152 to the reservoir. When the body 140 is shifted to the right by operation of the push knob 142, the exhaust line 152 is partially closed and the supply line 132 is partially connected with the supply line 148 from the reservoir 146 and gear pump 150 to supply fluid at a controlled pressure as determined by the amount theA member 142 is moved. The'piston 128 is thus biased to the left and acts through plunger 120 to deform the base 124 slightly thus imparting a slight increment of feedingmovement to the grinding wheel 44 and work referred to at 32 in Fig. 2.

in the preferred embodiment of the invention shown, the machine is provided with a work sizing gauge having associated therewith a visual meter and amplifier by means of which the operator is lable to tell at a glance to within a few millionths of an inch the actual size to which the work has been ground. A work size gauging device of this description is shown in Fig. 10 comprising a housing 164 having depending therefrom a back rest 166 and a vertically movable gauging plunger 1.68.

Movement of the gauging plunger 168 are reflected by theposition of a pointer on an amplifier unit 170 which is capable of magnification sufficient to enable the operator V'to readily observe changes in the position of the gauging plunger 168 to within millionths of an inch. Inasmuc'h as this apparatus is well known in the art, no further description or illustration of this mechanism is believed necessary herewith. The connection of the gauging device with respect to the present invention consists in the fact that the operator is provided Vwith visual inspection means which enables him to determine exactly how far the grinding operation has progressed, thus enabling the operator to continue the grinding operationand then to arrest the grinding operation when the work-has been brought exactly tothe desired size.v

In each vof the two embodiments of vthe invention illustrated the .grinding machine Vis provided with a base structure including a rigid unitary supporting member on which aregmounted a work table, and, rearwardly thereof, a grinding wheel carriage. A -feed mechanism which may be of a conventional type including a feed screw and nut is provided for moving the grinding wheel carriage andrgrinding wheel mounted-thereon to a finish grind-position. The supplemental feeding device provided in-accordance with the present invention acts Vin each of the embodiments shown to produce an elastic distortion Vof the vrigid 'unitary supporting member land thereby slight additional in'rer'rieiit offfed of the grinding wheel toward the work. This additional increment of feed is secured without affecting the final setting of the feed handwheel and feed screw and nut mechanism, and without changing the stresses and strains set up in the feed mechanism during the advance of the grinding wheel carriage to its final depth feed position. The final vincrement of feed obtained by the resilient distortion of the rigid unitary supporting member on which the work support and grinding wheel carriage are mounted is a fraction only of the smallest advance of the grinding wheel which may be obtained by jogging or inching ahead the cross feed handwheel, and permits of a more accurate finished grinding of the work to within a few hundred thousands or even millionths of an inch. .t t

For the operation of the machine the cross feed may be set to cause the4 grinding wheel to spark out while the work piece 32 vis still a few hundred thousands or millionths of an inch over size. The operator then presses a push button 106 or 142 as the case may be, .the amount of pressure exerted being gradually increased until the grinding wheel is brought to the precise nish position desired as indicated by the position of the pointer on the amplifier 170 of Fig. 10. The instant that the work is brought to size the operator will release the push button causing the grinding wheel to be quickly removed from the work as the stress onrthe machine frame is eased. It will be noted that this slight retracting movement of the grinding wheel is caused simply by a relaxation of the elastic stress imposed when the push button 106 was pressed, and thus eliminates all problems of run-out, sparking-out and the like which normally affect the operation of the tine feed of the ordi nary grinding machine to depth.

The invention having been described what is claimed is:

1. A ne feed control for a machine tool having a base structure comprising a rigid unitary supporting member, a work support mounted on a portion of said rigid unitary supporting member, a tool support mounted on a second portion of said rigid unitary supporting member, feeding means for one of said supports, means for effecting a continuing visually observable measurement of the work size, and supplemental operator-controlled means for effecting a resilient deformation of said rigid unitary supporting member to move said first and second portions of said rigid unitary supporting member, and said work support and tool support mounted thereon, relatively in the direction of said feed to an extent adjustable in accordance with said visually observable measurement of the work size so that the portions of said supporting member supporting said tool support and work support are moved relatively in the direction of feed to effect a further controlled increment of relative feed of the said work support and said tool support in accordance with said visually observable measurement of the work size.

2. A fine feed control for a grinding machine having a base structure comprising a rigid unitary supporting member, a work support mounted on a forwardly disposed portion of said rigid unitary supporting member, a tool support mounted rearwardly of said work support on a rearwardly disposed portion of said rigid unitary supporting member, feeding means for effecting a movement of one of said supports relative to the other of said supports, means for effecting a continuing visually observable measurement of the work size, and supplemental means for causing a further relative approach movement between said supports which comprises an operator actuated device for exerting a distorting strain of adjustable extent upon said rigid unitary supporting member to move said forwardly disposed portion and said rearwardly disposed portion toward one another thereby effecting a resilient deformation of said rigid supporting iiember so that the portions of saidsupport ing member on which said work support and said tool support are mounted are moved relatively toward one another to effect a further controlled increment of ,relative feed of said work support and said tool support, in accordance with the visually observed movement of the work size. t

3. A fine feed control for a grinding machine having a base, a bed comprising a rigid unitary supporting member, a work support mounted on a forwardly disposed portion of said rigid unitary supporting member, a tool support mounted rearwardly of said work support on a rearwardly disposed portion of said rigid unitary supporting member, feeding means for effecting a movement of one of said supports relative to the other of said supports, and supplemental feeding means for causing further-f relative `approach movements between said supports which comprises a devicefor exerting a distorting strain upon said rigid unitary supporting member thereby effecting a resilient deformation of said rigid supporting member to move said forwardly disposed portion and said rearwardly disposed portion toward one another to move said supports relatively in the direction of said feed so that the portions of said supporting member on which said work support and said tool support are mounted are moved relatively to effect a further increment of relative feed of said work support and said tool support, a manually operable element mounted on the` machine and connected with said device for exerting a distorting strain upon said rigid unitary supporting member so that pressure exerted upon said manually operable element acts through said device to effect a further increment of relative feed of said work support and said tool support and the release of said manually operable element releases the distorting strain to remove said resilient deformation and thereby effects a separating movement of said work support from said tool support.

4. A fine feed control for a grinding machine having a base, a bed comprising a rigid unitary I.supporting member having a three-point support on the base, a work support mounted on a forward portion of said bed, a tool support mounted on said bed rearwardly of the work support, feeding means for effecting movement of one of said supports relative to the other, means for effecting a continuing visually observable measurement of the work size, and a supplemental feeding means for causing approach movement between said supports which comprises a traction device connected between a portion of the bed intermediate said points of support and the base, a manually operable element mountedon the machine, and means actuated by said manually operable element for actuating the traction device including a pressure applying means connected between the manually operable movement and said traction device operabl to apply a controlled force to said traction device to effect a resilient distortion of the bed and thereby to cause a further relative -feeding approach movement between said supports in accordance with the visually observed measurement of work size.

5. A ne feed control for a grinding machine having a base formed with a knee-hole recess, a bed comprising a rigid unitary supporting member and having a threepoint support on the base formed with a knee-hole recess overlying said knee-hole recess in the base, two points of support for said bed on the base being located at the opposite sides of said recesses and the third point of support for the bed on the base being located rearwardly of the recess, a work support mounted for traversing movement on a forwardly disposed portion of said bed over said recesses, a grinding wheel carriage mounted for forward and back movement on the bed rearwardly of said work support, feeding means for the grinding wheel support, and a device connected between the recess portions of said bed and base operable to bias said recess portion of the bed downwardly toward the baseto effect a downward distortion of-said-recessed portion-ofthe bed, 'and thereby an'additional increment of feeding movement of the grinding wheel support relative to the work^'supp'ort.

`6. yA -n'efeed control for 'afgrinding machine in `acco'rdancewith claim `5 in `which `the device to bias said recess portion of the bed downwardly toward-the base comprises fapost secured to the -recess Lportion of the base 'and extending upwardly -into the recessedportion of the bed, -a-fulcrum lever-mounted in the recessed portion of :the bed arranged-for engagement 'with said post, a spring 'arm secured to said fulcrum lever and amanually operable controlelement connected with and-arranged toact upon vsaid spring 'ar-m to -bias the fulcrum lever-in a direction to-effect a resilient deformation -of the-bed and thereby toproduce tan additional increment of--feedingmbve'ment of Athe grinding' wheelcarriage' relative lto the work support.

7. VA fine feed control-for -a grinding machine having a basev structure comprising a rigid unitary supporting member, a work support mounted on a forwardly disposed portion of said rigid unitary supportingv member, a tool support mounted rearwardly of said work'support on -a rearwardly disposed portion of said rigid unitary supporting member, feeding means for'effectinga movement of one of saidsupports relative to the-other of said supports, and a supplemental feeding means-for causingy relative approach movement vbetween said supportsl which comprises va --distortion producing device connected ibetween portions of fsaid rigid unitary "supporting member adapted when actuated 'to effect aresilient deformation of said rigid unitary supporting member to movefsaid forwardly disposed portion and said rearwardly disposed portion toward-one-another to move said'supports relativelyin the direction'of feed'so that portions of :said supporting member on which said work support and said tool support are mounted are moved relatively to effect a further increment of relative -feed of said work support and said tool support, said distortion 4producing device comprising a fiuid pressure cylinder connected between said portions on theri-gid unitary supporting member, means --for supplying la uid under pressure'to saiduid pressure cylinder, :a manual control shiftable between an off fandxopen position to direct iuid under vpressurezto said fluid pressure cylinder and thereby applying .pressure between said'por-tions-to effect 1a 'distortion ofasaid rigid unitary'-supportingmember, and yieldably acting means -for-returningisaid manual'control to said olf .position in which said distortion of the rigid unitary supporting member is eliminated.

References Cited inthe file 'of this patent UNITED STATES PATENTS 

